This invention relates generally to the confinement of material in a porous medium in the earth, especially for containing hazardous wastes, and more particularly to providing such confinement by heating a limited region of the earth to drive off water and replacing the water with a sealant.
Hazardous waste materials have been improperly deposited in thousands of sites all over the United States and, indeed, all over the world. Uncontrolled landfills have been used as convenient, but inadequate, disposal sites for industrially generated wastes, while other sites have been contaminated by accidental spills of hazardous materials. There are also conditions where hazardous materials are stored or carried in confining tanks, pipes or ditches where the confining walls may leak materials into the earth. There are many sites where hazardous materials were spilled prior to the discovery of the hazardous nature of the materials being handled. Many hazardous materials are difficult to dispose of because they are stable, do not undergo environmental degradation at reasonably fast rates, have high boiling points, are considered toxic at very low concentration levels, and/or bioaccumulate in various species of the food chain at concentrations higher than that naturally occurring in the environment.
A common way of dealing with hazardous waste deposited in the earth has been to excavate the site and incinerate the materials to destroy the hazardous waste. This solution has proven relatively impractical in many cases because of the high cost of excavation and incineration, the shortage of incineration capacity, inadequate methods and capacity for ash disposal in the incinerators, and the hazards and risks associated with site disturbance and transportation.
One alternative to excavation has been the in situ decontamination of waste as shown in Bridges et al. U.S. Pat. No. 4,670,634, wherein radio frequency heating applied to the sites is used to render the materials innocuous, as by pyrolyzing noxious materials or driving off effluents that can be captured and incinerated.
An alternative to removing the hazardous wastes has been to contain them. One such containment scheme is shown in Brouns et al. U.S. Pat. No. 4,376,598 which shows conduction heating to very high temperatures of radioactive components in soil, the soil being heating to vitrification at temperatures as high as 1500.degree. C. At such temperatures radioactive contaminants are fused with the silicates in the soil to form a glass or similar product which, upon cooling, forms a stable mass. It is also known to encapsulate hazardous material in impervious materials, as shown in Valiga U.S. Pat. No. 4,375,930.
It is known to isolate a volume of the earth by drilling holes around the volume and pumping down grouting to form a barrier, as shown in Lyons et al. U.S. Pat. No. 4,311,340. It is also known to form a structure beneath the surface of the earth, without excavation, by injecting cement at appropriate places, as shown by Harris U.S. Pat. No. 528,367. Muller U.S. Pat. No. 3,688,507 also discloses a method for providing barriers by forcing grouting into regions where the barriers are to be created. Levy et al. U.S. Pat. No. 3,608,318 discloses a method and apparatus for injecting hot asphalt into relatively permeable earth formations to form water impervious dikes.